Vigano, 75, said he told Francis about claims of sexual abuse against Cardinal Theodore McCarrick, the former archbishop of Washington DC, on June 23, 2013, shortly after he became pope. McCarrick resigned last month over claims he sexually abused seminary students and an alter boy.

Vigano ended his statement with a call for the head of the Catholic church to step down and “acknowledge his mistakes and, in keeping with the proclaimed principle of zero tolerance, Pope Francis must be the first to set a good example to Cardinals and Bishops who covered up McCarrick's abuses and resign along with all of them,” he writes.

In the statement, Vigano said he told Francis that the Congregation for Bishops had a “dossier this thick” about McCarrick. “He corrupted generations of seminarians and priests and Pope Benedict ordered him to withdraw to a life of prayer and penance," Vigano added.

The former ambassador says the pope did not respond to his plea and said McCarrick was left to continue his role in the church. The former archbishop says the pope must now “honestly state when he first learned about the crimes committed by McCarrick, who abused his authority with seminarians and priests”.

On Saturday, Francis met with survivors of clerical sex abuse in Ireland and referred to people who cover up child abuse in the Catholic Church as “caca,” a Spanish word which the official translator interpreted as “filth you would see in the toilet.”

“The failure of ecclesiastical authorities — bishops, religious superiors, priests and others — to adequately address these repugnant crimes has rightly given rise to outrage, and remains a source of pain and shame for the Catholic community,” the pontiff said. “I myself share these sentiments.”

On Sunday, hundreds of people staged a ‘Stand4Truth’ march in Dublin in support of victims of clerical abuse as a counter-event to coincide with Pope Francis’ mass in the city. Protesters are calling on the pope to apologize for abuses perpetrated by clergy and concealed by church leaders, and for records to be passed on to a criminal investigation.

On LUAS to Dublin to stand in solidarity with those hurt by clerical abuse, to call for transparency, for justice, for truth. Archives and records held in the Vatican and also locally MUST be released to the civic authorities; otherwise apologies are meaningless#Stand4Truthpic.twitter.com/7HhgDLtNkl